WASHINGTON, March 22 (Reuters) - Julius Genachowski said on Friday he will step down as chairman of the U.S. Federal Communications Commission in the coming weeks after four years on the job, and touted his record of working to expand broadband Internet service to Americans.

Genachowski, whose term was due to end in June, told FCC staffers he would be leaving his post “in the coming weeks” but did not give a date. He told Reuters after his announcement that he has no career plans lined up for after his FCC tenure ends.

“I‘m still focused on the work of the agency,” Genachowski said, adding that he expects the FCC, which maintains a Democratic majority, to keep its policy direction after he leaves.

Asked to describe his tenure at the FCC in three words, Genachowski answered “unleashing broadband’s benefits.”

His exit from the agency that oversees telecommunications and broadcast policies was widely expected after President Barack Obama’s re-election. Obama will nominate a successor to Genachowski, who has headed the FCC since 2009.

In a statement, Obama praised Genachowski, the president’s classmate at Harvard Law School, for giving the FCC a “clear focus” on encouraging innovation and competitiveness, attracting “jobs of tomorrow” and improving high-speed Internet access and mobile devices sector growth.

“I am grateful for his service and friendship, and I wish Julius the best of luck,” Obama said.

The FCC is also losing its senior Republican commissioner. Robert McDowell said on Wednesday he will depart his post in a few weeks, leaving the five-member panel with two Democrats, one Republican and two vacancies.

Among the possible candidates to head the FCC is Tom Wheeler, a venture capitalist and an Obama ally and fundraiser. Wheeler headed the National Cable Television Association and the wireless industry group CTIA.

Two other possible contenders are: Lawrence Strickling, head of the National Telecommunications and Information Administration, which advises the president on telecommunications and information policy; and Karen Kornbluh, the U.S. ambassador to the Organization for Economic Cooperation and Development, an international economic body.

The next FCC chief faces a list of projects to complete. One major one is Genachowski’s plan for a complex incentive auction of spectrum that is meant to free up airwaves for better wireless Internet access.

The auction relies on TV stations to give up some of their airwaves to be auctioned off to wireless companies or opened up for shared use. The broadcasters would get a portion of the proceeds and the rest would pay for a public-safety program and go to the U.S. Treasury.

Also on the list is the delayed loosening of rules on media ownership.

Asked whether he would like to see a vote on those rules before he leaves the FCC, Genachowski said only that the commission will “continue to work on the agenda.”

Later this year, a federal court will also hold hearings in a case against Genachowski’s net neutrality rules for Internet service providers that could have broad implications for the breadth of the FCC’s regulatory power.

‘AN UNEASY DANCE’

In his FCC tenure, Genachowski oversaw an overhaul of the multibillion-dollar Universal Service Fund from a project to spread telephone service in rural America to one focused on broadband access. He also spearheaded the creation of a strategy known as the National Broadband Plan and later pushed Internet providers to step up the speediness of their services.

The FCC’s priorities under Genachowski reduced the influence of U.S. broadcasters, the relationship with whom has been “an uneasy dance,” according to Medley Global Advisors telecommunications policy analyst Jeffrey Silva.

Also left disappointed were liberal-leaning organizations including consumer interest groups. Harold Feld of advocacy group Public Knowledge said Genachowski is leaving more tasks for his successor to finish than most of his predecessors.

“It’s true to some degree of every chairman, but this chairman in particular came in with a lot of expectations,” Feld said. “And then, as people say, he wrote a lot of checks that he’s now leaving for the next chair to figure out how to cash.”

Genachowski, who charted a centrist course in his chairmanship, defended his tenure, which also included the FCC’s rejection of a landmark 2011 merger bid between U.S. No. 2 wireless carrier AT&T Inc and fourth-largest provider T-Mobile USA, a unit of Deutsche Telekom. The bid was dropped after the Justice Department sued to block the deal.

In pushing against the merger, Genachowski stood up against the prospect of a duopoly in the wireless market by AT&T and the largest carrier, Verizon, analysts say, as it retained T-Mobile as a competitor and protected the third-biggest player Sprint from being overwhelmed.

“This sector has always been and will always be characterized by a robust debate,” Genachowski said.

“Some people say the commission has gone too far, some people say the commission hasn’t gone far enough. What we’ve been focused on are the right actions to drive the economy and to improve the lives of the American people.”

Genachowski came to the FCC after advising Obama on telecommunications policy and working at several tech investment firms. He had previously served as chief counsel for former FCC Chairman Reed Hundt.